# -*- coding=utf-8 -*-
# 给定一个包含 0, 1, 2, ..., n 中 n 个数的序列，找出 0 .. n 中没有出现在序列中的那个数

# 示例 1:
# 输入: [3,0,1]
# 输出: 2

# 示例 2:
# 输入: [9,6,4,2,3,5,7,0,1]
# 输出: 8

class Solution(object):
    def missingNumber(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        n = len(nums);
        sum_all = n * (n + 1) / 2;

        return sum_all - sum(nums);

t = Solution();
print t.missingNumber([9,6,4,2,3,5,7,0,1]);